The ability to switch between open files (CTRL+Tab) or close an open file (CTRL+W), similar to how modern browsers works, would be extremely nice for when users are quickly looking back and forth between 2 different files on a single screen.
Also, CTRL+N to start a new document would be pretty nice as well.
It may seem like nothing to click a tab, but when you are trying to compare features or simulation results quickly on a laptop, clicking between tabs with a trackpad can be difficult.